[CALCITE-2755] expose document _id field when querying ElasticSearch

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.19.0
• Component/s: elasticsearch-adapter
• Labels: pull-request-available
• Assignee: Julian Hyde
• Reporter: Andrei Sereda
• Created: 26/Dec/18 20:43
• Updated: 03/Jan/19 00:31
• Resolved: 02/Jan/19 19:42

Description

Elastic exposes _id field for each document (think unique doc ID).

Expose if it is explicitly listed in projection: 

select _MAP['_id'], _MAP['foo'] from elastic -- available
select * from elastic -- not available

Issue Links

• links to: PR 982